In recent years, as for a liquid crystal display device, with the expansion of applications and the enhancement in functionality, high reliability and durability are expected for an individual device constituting the liquid crystal display device. For example, in a case of a transmission type liquid crystal projector which uses a light source with a large amount of light, a polarization conversion element configured to convert the natural light emitted from the light source into linearly-polarized light receives strong radiant rays. Therefore, if the durability of the polarization conversion element is low, the illumination efficiency will decrease.
The polarization conversion element usually includes a polarizing beam-splitter array formed by alternately bonding a polarizing beam splitter with a polarization separation film and a prism with a reflective film, wherein a phase difference plate is selectively provided above the output surface of the polarizing beam splitter.
Conventionally, as the phase difference plate selectively provided above the output surface of a polarizing beam splitter, a dichroic phase difference plate containing an iodine-based or dye-based polymer organic matter in a film is often used. As the general manufacturing method of the dichroic phase difference plate, there is adopted a method of performing dyeing using dichroic material such as a polyvinyl alcohol-based film and iodine, and then performing cross-linking using a cross-linker to perform uniaxial stretching. The phase difference plate including such a stretched polymer film is likely to deteriorate by heat and/or UV light, and is therefore poor in durability. Moreover, this type of phase generally shrinks easily, because it includes a stretched polymer film fabricated by stretching. Moreover, the polyvinyl alcohol-based film is very likely to deform particularly under a humidified condition because of using a hydrophilic polymer, and is therefore poor in mechanical strength as a device. In order to solve this problem, a phase difference element of an inorganic optical single crystal, such as a crystal, may be used, but it has the drawbacks that an increase in size is difficult and that the raw material cost and processing cost are also high.